Amplifier coupling



July 14, 1931. H. P. DONLE AMPLIFIER COUPLING Filed Feb. 19, 1927 Patented July 14,1931

UNITED STATES,

PAITiEQNr OFFICE".

HAROLD P. DONLE, on MER-IDEN, CONNECTICUT, ASSIG'NOR, ,IBY MESNE ASSIGNMENTS;

T0 RADIO rnvnn'rrons, II\TG., A ooiaroiaerronor NEW YORK i AMPLIFIER COUPLING Application filed February 19, 192?. 'seriarno. 169,553;

The main object of my invention is to produce a coupling for audio frequency amplifiers which will give a high quality of reproduction.

Another object is to produce a coupling device with which substantially uniform amplification may be attained over the entire musical scale;

Another object is to produce a coupling device of high efficiency.

In the drawing, I have shown a three stage amplifier employing my novel coupling device. The closed iron core 5 carries a primary winding 6 which is connected between the anode 7 of the vacuum tube 8 and the positive terminal of the B battery. The core 5 also carries on opposite legs the two similar secondary windings 9 and 10. The lower ends of these two windings are connected to the cathode 11 of the vacuum tube 12' and the upper ends are connected together by the condenser 13. The upper end of the winding 10 which is on the leg opposite that carrying primary winding 6 is connected to the grid or control electrode 14 of the tube 12.

The coupling devices 15 and 16. used in the first and third stages are those more fully described and claimed in my copending application #98,4L51 and consist of combined inductive and capacitative means for energy transfer.

The damping resistance 17 servesto prevent internal oscillation withoutappreciable loss of signal strength as described and claimed The turn ratio between the primary winding and the two secondary windings may be of the order 4 to 1, but this ratio may be Varied considerably to meet the requirements in my co-pending application of amplification or of the associated tubes.

The condenser 13 preferably has a value greater than 0.025 inf, but may be varied to suit the transformer ratio. v

I have found that with the coupling device described above the high overall amplification usually present in a properly designed transformer of fairly high ratio is attained and at the same time the high quality of reproduction generally associated with low ratio transformers and impedance coupling 15 maintained. I

I believethis to'be due in measure to the I large number of natural periods presentin' the various closed circuits; Forins tance the clrcuit consisting of the inductances 9 and 10 and the condenser 13 has a very low'periodf near the bottom of the musical scale, 'Ih'e circuit formed by theinductance 10and the capacity between the grid 14; and the filament 11 hasfla higher period. The primary inductance 6 and the anode-cathode capacity of the tube 8 forms a circuit having a still higher period.

A system consisting of several closely-coupled circuits of differing periods possesses as a .whole a very large number of periods. I believe that this large number of periods is presentin my coupling device and accounts for the high and uniform amplification obtained throughout the entire musical scale.

I claim:

1. An audio frequency interstage coupling device comprising a rectangular iron core, said core carrying three windings, one of said windings being connected between the anode and the anode supply source of a vacuum tube, said circuit having a high natural oscillatory period, the other two of said wind ings having common connections to the cathode of another vacuum tube and common connections to the control'electrode of said latteryacuum tube, one of said latter connections being made through a capacitance, said circuits having medium and lower nat-v ural oscillatory periods and having materially dilferent degrees of electromagnetic coupling with respect to the first mentioned circuit, whereby the distribution of energy transfer can be apportloned 1n the two latter circuits according to a desired ratio.

2. In combination an audio frequency coupling device and a triodic amplifier tube,

ferring their energy to the input circuit of said triodic amplifier tube, the one winding transferring through a direct conductive connection and the other through an interposed condenser, said latter two windings and their connections constituting two electrical circuits of different oscillatory periods and in difierent energy absorbing relationship to said first winding.

3. A vacuum tube coupling device comprising a primary winding for the energy input of the device, two secondary windings electromagnetically coupled with substantially difi'erent degrees of coupling to the primary winding, a conductor making connection to one end of each secondary winding and constituting one terminal of the output circuit of the device, a condenser with one terminal connecting to the opposite end of the first secondary winding and a conductor making connection to the other terminal of the condenser and the other end of the second secondary winding and constituting the other terminal of the output'circuit of the device.

HAROLD P. DONLE. 

